A young member of my forum who is relatively new to monarchism asked how he could defend the "lavish lifestyles" of ancien regime royalty and aristocracy. As this is a question that often comes up in discussions of monarchy I thought I'd also post my own response here, while encouraging visitors to read others' answers at the original thread as well.
First of all, Marie Antoinette never said "let them eat cake"; that was revolutionary propaganda.
This article is a good start:
It is true that there was certainly inequality in the era of the monarchies, but there is also inequality today in democracies and republics. Many of the improvements in quality of life we take for granted today are the results of technological and medical advances that have benefited everyone; in many ways the life of a "poor" person in France today is more comfortable than that of an 18th-century French king.
There always have been and always will be "haves" and "have nots," and I think it's better to be honest about it as a formalized class system is. Ironically, generally the monarchs who have been blamed for Revolutions were themselves genuinely compassionate and charitable and did what they could to alleviate the suffering of the less fortunate. This was certainly true of Louis XVI and Marie Antoinette.
A perhaps more important point, though, is that the existence of so-called "lavish lifestyles" is a good and necessary thing, even for those not able to live them themselves. This may seem a shocking thing to say, but think about it: many non-wealthy people depend, and have depended throughout history, for their very livelihoods on professions and trades that could not exist without "lavish lifestyles." Think of manufacturers of luxury goods and those who supply their materials. Think of chefs creating gourmet delicacies, and those who supply their ingredients. Think of architects of palaces and mansions and those who work on building them, and those who supply their materials. Think of artists who in order to make a living from painting must charge prices for their work that no one of limited means could possibly afford. And of course, think of those of my own profession, musicians, who have relied on the patronage of wealthy people, now almost as much as then, though the form of such patronage has changed. Public concerts as we know them today did not exist in the 18th century and before; if there had been no royalty and aristocrats able to afford their own court orchestras (part of that much-maligned "lavish lifestyle"), no one could have earned a living as a secular musician, as I like to imagine myself doing had I lived in a previous era.
Therefore, it is an economic fallacy to assume that the lavish lifestyles of royalty and aristocracy caused poverty. Rather, there would have been even more poverty if the ordinary people in the professions described above had not been able to indirectly benefit from the economic activity generated by those lavish lifestyles. This has been proved time and time again by the results of the egalitarian revolutions that have attempted to eliminate the luxury of privileged classes: more misery and suffering for everyone.